/*

 * Copyright (c) 2015, 2018, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

package jdk.internal.net.http;

import java.io.IOException;

import java.io.UncheckedIOException;

import java.net.ConnectException;

import java.net.InetSocketAddress;

import java.net.URI;

import java.util.Base64;

import java.util.Collections;

import java.util.HashSet;

import java.util.Map;

import java.util.Set;

import java.util.concurrent.ConcurrentHashMap;

import java.util.concurrent.CompletableFuture;

import jdk.internal.net.http.common.Log;

import jdk.internal.net.http.common.Logger;

import jdk.internal.net.http.common.MinimalFuture;

import jdk.internal.net.http.common.Utils;

import jdk.internal.net.http.frame.SettingsFrame;

import static jdk.internal.net.http.frame.SettingsFrame.INITIAL_WINDOW_SIZE;

import static jdk.internal.net.http.frame.SettingsFrame.ENABLE_PUSH;

import static jdk.internal.net.http.frame.SettingsFrame.HEADER_TABLE_SIZE;

import static jdk.internal.net.http.frame.SettingsFrame.MAX_CONCURRENT_STREAMS;

import static jdk.internal.net.http.frame.SettingsFrame.MAX_FRAME_SIZE;

/**

 *  Http2 specific aspects of HttpClientImpl

 */

class Http2ClientImpl {

    final static Logger debug =

            Utils.getDebugLogger("Http2ClientImpl"::toString, Utils.DEBUG);

    private final HttpClientImpl client;

    Http2ClientImpl(HttpClientImpl client) {

        this.client = client;

    }

    /* Map key is "scheme:host:port" */

    private final Map<String,Http2Connection> connections = new ConcurrentHashMap<>();

    private final Set<String> failures = Collections.synchronizedSet(new HashSet<>());

    /**

     * When HTTP/2 requested only. The following describes the aggregate behavior including the

     * calling code. In all cases, the HTTP2 connection cache

     * is checked first for a suitable connection and that is returned if available.

     * If not, a new connection is opened, except in https case when a previous negotiate failed.

     * In that case, we want to continue using http/1.1. When a connection is to be opened and

     * if multiple requests are sent in parallel then each will open a new connection.

     *

     * If negotiation/upgrade succeeds then

     * one connection will be put in the cache and the others will be closed

     * after the initial request completes (not strictly necessary for h2, only for h2c)

     *

     * If negotiate/upgrade fails, then any opened connections remain open (as http/1.1)

     * and will be used and cached in the http/1 cache. Note, this method handles the

     * https failure case only (by completing the CF with an ALPN exception, handled externally)

     * The h2c upgrade is handled externally also.

     *

     * Specific CF behavior of this method.

     * 1. completes with ALPN exception: h2 negotiate failed for first time. failure recorded.

     * 2. completes with other exception: failure not recorded. Caller must handle

     * 3. completes normally with null: no connection in cache for h2c or h2 failed previously

     * 4. completes normally with connection: h2 or h2c connection in cache. Use it.

     */

    CompletableFuture<Http2Connection> getConnectionFor(HttpRequestImpl req,

                                                        Exchange<?> exchange) {

        URI uri = req.uri();

        InetSocketAddress proxy = req.proxy();

        String key = Http2Connection.keyFor(uri, proxy);

        synchronized (this) {

            Http2Connection connection = connections.get(key);

            if (connection != null) {

                try {

                    if (connection.closed || !connection.reserveStream(true)) {

                        if (debug.on())

                            debug.log("removing found closed or closing connection: %s", connection);

                        deleteConnection(connection);

                    } else {

                        // fast path if connection already exists

                        if (debug.on())

                            debug.log("found connection in the pool: %s", connection);

                        return MinimalFuture.completedFuture(connection);

                    }

                } catch (IOException e) {

                    // thrown by connection.reserveStream()

                    return MinimalFuture.failedFuture(e);

                }

            }

            if (!req.secure() || failures.contains(key)) {

                // secure: negotiate failed before. Use http/1.1

                // !secure: no connection available in cache. Attempt upgrade

                if (debug.on()) debug.log("not found in connection pool");

                return MinimalFuture.completedFuture(null);

            }

        }

        return Http2Connection

                .createAsync(req, this, exchange)

                .whenComplete((conn, t) -> {

                    synchronized (Http2ClientImpl.this) {

                        if (conn != null) {

                            try {

                                conn.reserveStream(true);

                            } catch (IOException e) {

                                throw new UncheckedIOException(e); // shouldn't happen

                            }

                            offerConnection(conn);

                        } else {

                            Throwable cause = Utils.getCompletionCause(t);

                            if (cause instanceof Http2Connection.ALPNException)

                                failures.add(key);

                        }

                    }

                });

    }

    /*

     * Cache the given connection, if no connection to the same

     * destination exists. If one exists, then we let the initial stream

     * complete but allow it to close itself upon completion.

     * This situation should not arise with https because the request

     * has not been sent as part of the initial alpn negotiation

     */

    boolean offerConnection(Http2Connection c) {

        if (debug.on()) debug.log("offering to the connection pool: %s", c);

        if (c.closed || c.finalStream()) {

            if (debug.on())

                debug.log("skipping offered closed or closing connection: %s", c);

            return false;

        }

        String key = c.key();

        synchronized(this) {

            Http2Connection c1 = connections.putIfAbsent(key, c);

            if (c1 != null) {

                c.setFinalStream();

                if (debug.on())

                    debug.log("existing entry in connection pool for %s", key);

                return false;

            }

            if (debug.on())

                debug.log("put in the connection pool: %s", c);

            return true;

        }

    }

    void deleteConnection(Http2Connection c) {

        if (debug.on())

            debug.log("removing from the connection pool: %s", c);

        synchronized (this) {

            Http2Connection c1 = connections.get(c.key());

            if (c1 != null && c1.equals(c)) {

                connections.remove(c.key());

                if (debug.on())

                    debug.log("removed from the connection pool: %s", c);

            }

        }

    }

    void stop() {

        if (debug.on()) debug.log("stopping");

        connections.values().forEach(this::close);

        connections.clear();

    }

    private void close(Http2Connection h2c) {

        try { h2c.close(); } catch (Throwable t) {}

    }

    HttpClientImpl client() {

        return client;

    }

    /** Returns the client settings as a base64 (url) encoded string */

    String getSettingsString() {

        SettingsFrame sf = getClientSettings();

        byte[] settings = sf.toByteArray(); // without the header

        Base64.Encoder encoder = Base64.getUrlEncoder()

                                       .withoutPadding();

        return encoder.encodeToString(settings);

    }

    private static final int K = 1024;

    private static int getParameter(String property, int min, int max, int defaultValue) {

        int value =  Utils.getIntegerNetProperty(property, defaultValue);

        // use default value if misconfigured

        if (value < min || value > max) {

            Log.logError("Property value for {0}={1} not in [{2}..{3}]: " +

                    "using default={4}", property, value, min, max, defaultValue);

            value = defaultValue;

        }

        return value;

    }

    // used for the connection window, to have a connection window size

    // bigger than the initial stream window size.

    int getConnectionWindowSize(SettingsFrame clientSettings) {

        // Maximum size is 2^31-1. Don't allow window size to be less

        // than the stream window size. HTTP/2 specify a default of 64 * K -1,

        // but we use 2^26 by default for better performance.

        int streamWindow = clientSettings.getParameter(INITIAL_WINDOW_SIZE);

        // The default is the max between the stream window size

        // and the connection window size.

        int defaultValue = Math.min(Integer.MAX_VALUE,

                Math.max(streamWindow, K*K*32));

        return getParameter(

                "jdk.httpclient.connectionWindowSize",

                streamWindow, Integer.MAX_VALUE, defaultValue);

    }

    SettingsFrame getClientSettings() {

        SettingsFrame frame = new SettingsFrame();

        // default defined for HTTP/2 is 4 K, we use 16 K.

        frame.setParameter(HEADER_TABLE_SIZE, getParameter(

                "jdk.httpclient.hpack.maxheadertablesize",

                0, Integer.MAX_VALUE, 16 * K));

        // O: does not accept push streams. 1: accepts push streams.

        frame.setParameter(ENABLE_PUSH, getParameter(

                "jdk.httpclient.enablepush",

                0, 1, 1));

        // HTTP/2 recommends to set the number of concurrent streams

        // no lower than 100. We use 100. 0 means no stream would be

        // accepted. That would render the client to be non functional,

        // so we won't let 0 be configured for our Http2ClientImpl.

        frame.setParameter(MAX_CONCURRENT_STREAMS, getParameter(

                "jdk.httpclient.maxstreams",

                1, Integer.MAX_VALUE, 100));

        // Maximum size is 2^31-1. Don't allow window size to be less

        // than the minimum frame size as this is likely to be a

        // configuration error. HTTP/2 specify a default of 64 * K -1,

        // but we use 16 M  for better performance.

        frame.setParameter(INITIAL_WINDOW_SIZE, getParameter(

                "jdk.httpclient.windowsize",

                16 * K, Integer.MAX_VALUE, 16*K*K));

        // HTTP/2 specify a minimum size of 16 K, a maximum size of 2^24-1,

        // and a default of 16 K. We use 16 K as default.

        frame.setParameter(MAX_FRAME_SIZE, getParameter(

                "jdk.httpclient.maxframesize",

                16 * K, 16 * K * K -1, 16 * K));

        return frame;

    }

}